Gas lift system

ABSTRACT

An apparatus and system for alternately venting and lifting fluid from an accumulator in which the alternate connection of the accumulator with a vent and a gas source is controlled by the differential in pressure between two tubes, one of which contains well fluids and the other of which contains well fluids and into which a small quantity of gas is bled.

United States Patent 1151 3,659,961 Lamb et al. 1 May 2, 1972 [54] GAS LIFT SYSTEM 3,208,398 9/1965 13611 135 .417/115 1 3,523,744 8/1970 Holladay ...137/15s lnvenmrsl Charles Lamb; William Dudley 3.530.874 9/1970 Lamb eta] ..137/155 both of Dallas, Tex.; George S. Kingsley, Ventura, Califi; Edward E. DeMoss, Gar- Primary Examiner-Arthur T. McKeon land Assistant Examiner-Richard E. Gluck 73 Assignee: Teledyne, lnc., L05 Angeles, Calif. Attorney-l Vincent Martin. Joe 5 Edwards y.

fred H. Evans and Jack R. Springgate 221 Filed: Aug. 7, 1970 21 App]. No.2 61,943 [57] ABSTRACT An apparatus and system for alternately venting and lifting 52 us. 01 ..417/114,417/115,417/117 fluid from an accumulator in which the alternate Connection 51 1111. C1 ..F04f l/l8 of the accumulator with a vent and a gas Scum is Controlled [58] Field of Search ..417/1 14, 116, 146, 115, 1 17; by thedifferemial in Pressure between tubes, one Ofwhich 137 /1 5 5 contains well fluids and the other of which contains well fluids and into which a small quantity ofgas is bled. [56] References cued 11 Claims, 7 Drawing Figures UNITED STATES PATENTS 3,121,442 2/1964 Lamb etal. ..4l7/ll4X Ir /I 1 i L ?I 26 J9 r u 1-. /4z 1 22 i :1 1 5? :4J 5:: J2-\ k :44 35 h 27 \36 45 1 244 II/Z Patented May 2, 1972 2 SheetsSheet 2 Char/e1 f? [0/776 W/'///'0/77 A.

.Dud/ey Gear , INVENT R5 BYW GAS LIFT SYSTEM This invention relates to a system and apparatus for lifting fluid from a well and more particularly to a system and apparatus in which the pressure at the bottom of the well is periodically reduced to a low pressure.

An object of this invention is to be able to draw the bottom hole pressure of a producing well down to the minimum possible pressure or to a vacuum.

Another object is to alternately draw the bottom hole pressure of a producing well down to a minimum figure to induce flow of fluid from a formation and then inject lifting gas to lift such fluids in which the system is controlled by flow of fluids from the well.

Another object is to alternately draw the bottom hole pressure of a producing well down to a minimum figure and then lift the fluid which flowed from the formation in which the alternate drawing down of pressure and lifting steps are controlled by measuring the pressure differential between a tube having well fluid therein and a second tube having well fluid therein and into which a constant stream of gas is introduced.

Another object is to provide a gas lift system and apparatus in which the bottom hole pressure of a producing well is alternately drawn down to a minimum pressure and then lifted to the surface in which the transition from drawdown to lifting step, and vice versa, is controlled by a pressure gradient system in the well.

Another object is to provide a system in which a producing formation is vented to the surface to permit flow of fluid from the formation into the well and then the fluid is lifted to the surface by gas under pressure in which the alternate venting and pressurizing of the system is controlled by a valve which is shifted between two positions in response to a differential in two tubes, one containing well fluids and the other well fluids and gas.

Another object is to provide an apparatus and system as in the preceding object in which all of the working mechanism of the system is carried in a wireline retrievable body which is landed in a mandrel in the system.

Another object is to provide an accumulator for well fluids about the lower end of the production tubing of a producing well and to alternately vent and subject the accumulator to lifting gas to lift the accumulated fluids in which the alternate venting and lifting steps are controlled in response to differential in two tubes one of which contains well fluids and the other of which contains well fluids plus gas bled into the tube from the lifting gas source.

Another object is to provide a system and apparatus as in the preceding object in which the tube containing only well fluids is positively vented during the venting operation to insure proper operation of the system.

Other objects, features and advantages of the invention will be apparent from the drawings, the specification and the claims.

In the drawings, wherein an illustrative embodiment of this invention is shown, and wherein like reference numerals indicate like parts:

FIG. 1 is a schematic illustration of the lower portion of a producing well and apparatus in accordance with this invention for alternately venting and lifting fluids from the formation showing the main valve to be in lifting position;

FIG. 1A is a fragmentary schematic illustration of the control means of FIG. 1, showing the main valve to be in vent position;

FIGS. 2A and through 2D are continuation views partly in quarter section and partly in elevation, illustrating the wireline retrievable control apparatus shown schematically in FIGS. 1 and 1A;

FIG. 3 is a fragmentary sectional view of the power piston.

Referring to FIG. 1, the well is shown to have a conventional casing and packer 11 positioned in the casing just above the producing formation 12. A crossover mandrel indicated generally at 13 is carried by the packer 14. The annulus between the crossover mandrel and casing and the two packers 11 and 14 provide an accumulator for well fluid to flow from producing formation 12 into the accumulator space 15.

Above the packer 14 a production tubing 16 and a vent tubing 17 extend to the surface. The annulus between the two tubings 16 and 17 and the casing 10 provides a conduit for lift gas which is introduced through pipe 18.

In the production tubing 16 a standing valve 19 is provided which prevents down flow of fluids when gas is injected from the casing into the tubing 16 through one or more conventional gas lift valves indicated generally at 21 to lift well fluids. The well fluids above the standing valve 19 may be lifted to the surface in any conventional manner.

The control assembly indicated generally at 22 alternately connects the vent tube 17 and the high pressure gas from. lift gas conduit 23 with the accumulator space 15. During the time that the vent tube is connected with the accumulator space the pressure in the accumulator is reduced and thus the pressure on the formation 12 is reduced and well fluids flowing under this reduced back pressure condition flow through the standing valve 24 into the accumulator 15. When sufiicient fluids have accumulated, the control assembly 22 is operated to block the vent pipe 17 and connect the gas inlet conduit 23 with the accumulator space 15 to lift fluids from the accumulator through the ports 25 in the lower section of the dip tube 26 and thence up into the production tube 16 for lifting in the conventional manner with the gas lift valves 21.

In order to operate the control assembly, two tubes of fluid are utilized. One of these tubes is the dip tube 26, and the well fluids rising in the dip tube 26 during the time that the vent pipe is connected to the accumulator 15 provides a reference fluid. The second tube is provided by sensing tube 27 which has a volume reservoir 270 at its lower end. The clip tube and sensing tube are in fluid communication through the port 20 in the dip tube and are in fluid communication with the accumulator 15 through the ports 25.

A small constant flow of lifting gas is introduced into the sensing tube 27 in any desired manner to provide a reference tube containing gas. In the illustrated embodiment a bleed passageway is provided between the control assembly body indicated generally at 28 and the pilot valve stem 39. The changing difierentials in these two tubes are utilized to control the system.

Two-position valve member 29 is provided in the body 28 alternately communicating the vent tube 17 and the lift gas tube 23 with the accumulator 15. The valve member 29 cooperates with an upper seat 31 controlling the lift gas port and a lower seat 32 controlling the vent gas port to control communication of these ports with the accumulator 15. The lift gas port 33 communicates with the seat 31 through the passage 34. The vent gas port 35 communicates with the lower seat 32 through a passageway 36.

Means responsive to the differential between pressure in the dip and sensing tubes is provided for moving the main valve member 29 between its upper and lower positions where it cooperates alternatively with seats 31 and 32. This means may include a pressure responsive member such as the piston 37 which is exposed on its upper face to dip tube-production tubing fluid and on its lower face to gas in the sensing tube. The pressure responsive member 37 controls the operation of the main valve 29 through a pilot valve. This pilot valve includes the pilot valve member 38 carried on valve stem 39 which is in turn carried by the piston 37. The valve 38 cooperates with pilot valve seat 40 to open and close a passageway through the pilot valve seat 40 into the chamber 41. The pilot valve is urged toward closed position by a resilient member such as spring 42.

A second pressure responsive member such as the piston indicated generally at 43 is provided in the chamber 41. This piston is exposed on its upper face to pressure within the chamber 41 and on its lower face to lift gas pressure through the port 33. The piston 43 carries the main valve 29 on valve stem 44.

The two pressure responsive members and the main valve and pilot valve provide a means which is responsive to differentials in pressure in the dip and sensing tubes for altemately establishing fluid communication between the accumulator and the vent port and between the accumulator and the lift gas port.

In operation, with the parts as shown in FIG. 1, lift gas passes down from conduit 23 to port 33, past the main valve 29 and downwardly through passageway 45 into the accumulator 15. The standing valve 24 protects the producing formation from the pressure of the lift gas. The lift gas U-tubes fluid through ports 25 into the dip tube and lifts the well fluid in the accumulator up through the dip tube and production tube and past the upper standing valve 19. As soon as the pressure on opposite sides of the piston 37 is substantially equalized due to lifting of the hydrostatic head of well fluids in the production tubing, the spring 42 returns the pilot valve 38 to its seat. At this time, a bleed passageway (not shown) bleeds fluid from chamber 41 into the vent tube 17. This unbalances the forces across the piston 43 and the lift gas pressure at port 33 is effective on the lower side of piston 43 to move the piston 43 upward to thus open the vent port and close the lift gas port from communication with the accumulator 15. As there is a substantial differential in pressure across main valve 29 when it is seated on the lower vent seat 32, the main valve will move rapidly into engagement with the upper seat once the differential across the piston 43 overcomes this differential between the lift gas and vent port pressure. The parts will then be in the position shown in FIG. 1A.

Upon opening of the vent port, the accumulator is vented to the vent pipe 17 and fluid will begin to flow from the formation through the standing valve 24 into the accumulator 15. To be sure that the dip tube is vented, a standing valve 46 is provided to vent the dip tube in the event the liquid level in the lower level of the accumulator is such as to prevent complete venting of the dip tube.

While well fluids are rising in the accumulator and in the dip tube, a small amount of gas is constantly being metered into the sensing tube. Upon the liquid rising to a level to cover the port in the production tube, the pressure of the gas in the sensing tube will begin to reflect the pressure due to the hydrostatic head of liquid above the port 28 in the dip tube. As the hydrostatic head of liquid rises in the dip, it becomes effective on the piston 37. The gas in the sensing tube is at the same time effective on the lower surface of piston 37. The sensing tube and dip tube below the piston 37 provide essentially a U- tube and the gas in the sensing tube reflects the pressure resulting from the hydrostatic head of fluid in the dip tube. Upon the differential across the piston 37 being sufficient to overcome the force of spring 42, the pilot valve opens and per mits lift gas to enter the chamber 41 and, acting on the larger effective area on top of the piston 43, move the main valve 29 to its lower seat 32 to close the vent passageway and open the lift gas passageway. As there is a substantial differential across valve 29, it will move rapidly into engagement with seat 32 upon opening of the pilot valve 38.

Preferably, the body 28 carries the main and pilot valves and the two pistons and is wireline retrievable from the crossover mandrel 22 so that if the need arises the control assembly may be readily removed from the well for repair or replacement.

ln FIGS. 2A through 2D the preferred form of control assembly is shown. The body indicated generally at 28 includes a plurality of sections 28a through 281 which are secured together through suitable thread systems to form the body.

The body carries a plurality of packers to cooperate with the crossover mandrel and establish areas of communication between the body and the several different fluid conductors. In FIG. 2A the port 51 at the upper end of the body provides for communication of the upper surface of the upper piston 37 with the dip tube 26. The packer indicated generally at 52 isolates this port from the remainder of the control assembly. The packer 52 floats laterally upon the body section 28c to minimize alignment problems in fomiing the bore through the crossover mandrel.

Below the packer 52 ports 53 communicate with the sensing tube and the packer indicated generally at 54 cooperates with packer 52 to straddle the sensing tube port 53.

The lift gas ports 33 as well as ports 34 for conducting lift gas to the area of the pilot valve, are straddled by the packer 54 and a lower packer 55.

The packer 55 cooperates with a lower floating packer 56 to straddle the vent ports 35. The packer 56 is again of the floating type to minimize alignment problems.

In FIG. 2B the control bleed for bleeding lift gas into the sensing tube is shown. A tapered seat 59 is carried by the body section 28c and a spherical ball 61 is in sealing engagement therewith. The ball has a bore therethrough for receiving the stem section 39b. The bore through the ball and the adjacent stem section are finely polished and these polished sections provide a controlled orifice for leaking lifting gas into the sensing tube. The ball 61 is held on its seat by spring 42 and carrier 63. Reciprocation of the stem with operation of the pilot valve prevents clogging of the passageway between the stem and ball.

The pilot valve stem is broken into two sections 390 and 39b. They are connected together by head 57 carried on the lower stem section 39 which floats within a cage 58 carried on the upper stern section 39a.

The provision of the universal joint by the parts 57-58 avoids eccentricity problems between the piston 37 and the ball 61 and seat 59.

In the preferred form, the bleed from the chamber 41 to the vent pipe is provided by a passageway 64 extending through the main valve stem 44 and down through the main valve 29.

Above and below the main valve seats 31 and 32 a plurality of spring washers indicated generally at 65 and 66, respectively, provide shock absorbers to absorb the shock of closing action of the main valve on the valve seats.

In the preferred form, a novel piston 43 is utilized. The piston 43 includes the upper end of shaft or stem 44. A sleeve 43a is slidably mounted on stem 44. An O-ring 43b seals therebetween. The outer periphery of sleeve 43a has a fumeconical section 430 intermediate the ends of the sleeve. A seal member 430' of tetrafluoroethylene surrounds the sleeve and has a mating frusto-conical section. An O-ring 43c seals between the sleeve and seal ring and prevents pressure fluid from entering between the sleeve and seal ring. A support and guide member 50 is carried by stem 44 and has a sliding fit with the small upper end of sleeve 43a. The member 50 abuts the large end of the seal ring 43d. A wiper ring 43f of tetrafluoroethylene may be carried by the member 50 to prevent scoring of the wall of chamber 41.

The guide ring assures centering of the piston 43 and prevents failure of the seal at high pressure which would occur if the piston moved laterally out of its concentric relationship with the wall of chamber 41.

By arranging the seal member so that the pressure differential thereacross is always applied to the large end of the sleeve, less extrusion problems are encountered. The sleeve applies pressure upwardly to the seal 43d and a gradient is thus induced across the seal which decreases toward the large end of the seal. This end of the seal is stronger and more able to stand stresses. Thus the lowest extrusion pressure is exerted at the thickest portion of the seal and minimum extrusion results.

The preferred form of valve is functionally identical to the valve shown schematically in FIGS. 1 and 1A and operates in the same manner. Fluid from the production string is efiective on the upper piston 37 through the port 51. Fluid from the sensing tubing is efl'ective through the port 53 on the lower face of the piston 37. The pilot valve is urged downwardly by the spring 42 and when the force due to pressure in the sensing tube is sufficiently greater than the force due to pressure in the production tube, the pilot valve is moved to its open position. As the pilot valve 38 moves off its seat 40, fluid flows past the passageway 64 due to the bleed restriction 69, and easing pressure is effective on the piston 43 to move the piston downwardly to close the vent passage by seating of the main valve 29 on seat 32. Lifting gas then flows downwardly from port 33 through passage 45 and into the accumulator.

After the fluid has been lifted from the accumulator and forces due to pressure are equalized across the piston 37 sufficient that the spring 42 closes the pilot valve 38, the pressure within the chamber 41 reduces to vent pressure and the main valve 29 moves to engage the upper seat 31 due to the lift gas pressure being present on the bottom of the piston 43. When this occurs, the vent tube communicates through ports 35 and passageway 36 with the passageway 45 below the main valve 29 to vent the accumulator.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.

What is claimed is:

l. A gas lift apparatus comprising,

an accumulator,

a standing valve permitting flow of fluid into said accumulator,

a dip tube and a sensing tube in fluid communication with each other and with said accumulator, said dip tube providing for discharge of fluid from said accumulator,

means for bleeding a small amount of gas into said sensing tube,

a body having a vent port and a lift gas port, said lift gas port adapted to be connected to a source of pressurized gas, said vent port adapted to vent said accumulator, and

means responsive to the differentials in pressure in said dip and sensing tubes for alternately establishing fluid communication between said accumulator and said vent port and said accumulator and said lift gas port, whereby alternatively gas in said accumulator is vented and fluid in said accumulator is discharged.

2. The apparatus of claim 1 wherein said means responsive to a differential comprises,

a pressure responsive member exposed on one side to fluid in said dip tube and on the other side to fluid in said sensing tube, and

valve means shiftable between two positions in response to movement of the pressure responsive member to alternately connect the accumulator with the vent and lift gas ports.

3. The apparatus of claim 1 wherein a check valve in the dip tube adjacent the top of the accumulator permits flow of fluid from the dip tube to the vent port.

4. The apparatus of claim 1 wherein said means responsive to a differential comprises,

a pressure responsive member exposed on one side to fluid in said dip tube and on the other side to fluid in said sensing tube,

a pilot valve member carried by the pressure responsive member and cooperable with a seat to control flow of gas from said lift gas port through said seat,

a second pressure responsive member exposed on one side to said lift gas port and on the other side to said pilot valve seat,

bleed means for bleeding fluid from the other side of said second pressure responsive member to said vent port when said pilot valve is closed, and

two-position main valve means responsive to movement of said second pressure responsive member for alternately opening and closing said vent and lift gas ports.

5. The apparatus of claim 4 wherein a mandrel is associated with said clip tube and a wire line retrievable housing carries said pressure responsive members and said main and pilot valves.

6. A gas lift system comprising,

a well having three conduits therein providing a production tubing and a vent tubing and a lift gas conduit,

a crossover mandrel interconnecting the lower ends of the three conduits,

a dip tube communicating with the lower end of the production tubing and extending downwardly therefrom,

a sensing tube extending downwardly from the mandrel,

means for bleeding a small amount of gas from the lift gas conduit into the sensing tube,

an accumulator containing at least a portion of said dip tube and sensing tube,

said accumulator communicating with the producing formation through a standing valve and with said mandrel,

means establishing communication between said clip and sensing tubes within said accumulator,

two-position valve means in said mandrel alternately communicating said vent tube and said lifting gas conduits with said accumulator, and

means responsive to the differentials in pressure in said dip and sensing tubes at said mandrel for moving said valve means between said two positions.

7. The system of claim 6 wherein a check valve in the dip tube adjacent the top of the accumulator permits flow of fluid from the dip tube to the vent tube.

8. The system of claim 6 wherein the two-position valve means is responsive to a pressure responsive member which is exposed on one side to the lift gas conduit and on the other side to a chamber,

a pilot valve is carried by said means responsive to a differential and controls flow of lifting gas to said chamber, and

a bleed establishes communication between said chamber and said vent tube to bleed gas from said chamber when said pilot valve is closed.

9. The system of claim 8 wherein the pressure responsive member, the means responsive to a differential, the pilot valve and the two-position valve means are carried in a wire line retrievable housing in said mandrel.

10. The apparatus of claim 1 wherein the means for bleeding a small amount of gas comprises,

a tapered seat,

a spherical ball having a bore therethrough,

resilient means holding said ball on its seat,

and a stem extending through said bore in nonseating engagement therewith to leak a small amount of gas thereby,

said stem reciprocating each time fluid communication is shifted between said vent and lift ports to prevent clogging of the passageway between said stem and bore through the ball.

11. The apparatus of claim 4 wherein said second pressure responsive member comprises,

a shaft,

a sleeve slidable on the shaft,

means sealing between the sleeve and shaft,

said sleeve having a frusto-conical section,

a seal member of tetrafluoroethylene surrounding said sleeve,

said seal member having a frusto-conical bore section mating with said like section of said sleeve,

means sealing between the large end of said sleeve and said seal member,

and a support and guide ring carried by said shaft in sliding engagement with the small and of said sleeve and in abutment with the large end of the seal member,

said second pressure response member arranged so that the pressure differential thereacross is always applied to the large end of said sleeve.

i i i i I 101034 man 

1. A gas lift apparatus comprising, an accumulator, a standing valve permitting flow of fluid into said accumulator, a dip tube and a sensing tube in fluid communication with each other and with said accumulator, said dip tube providing for discharge of fluid from said accumulator, means for bleeding a small amount of gas into said sensing tube, a body having a vent port and a lift gas port, said lift gas port adapted to be connected to a source of pressurized gas, said vent port adapted to vent said accumulator, and means responsive to the differentials in pressure in said dip and sensing tubes for alternately establishing fluid communication between said accumulator and said veNt port and said accumulator and said lift gas port, whereby alternatively gas in said accumulator is vented and fluid in said accumulator is discharged.
 2. The apparatus of claim 1 wherein said means responsive to a differential comprises, a pressure responsive member exposed on one side to fluid in said dip tube and on the other side to fluid in said sensing tube, and valve means shiftable between two positions in response to movement of the pressure responsive member to alternately connect the accumulator with the vent and lift gas ports.
 3. The apparatus of claim 1 wherein a check valve in the dip tube adjacent the top of the accumulator permits flow of fluid from the dip tube to the vent port.
 4. The apparatus of claim 1 wherein said means responsive to a differential comprises, a pressure responsive member exposed on one side to fluid in said dip tube and on the other side to fluid in said sensing tube, a pilot valve member carried by the pressure responsive member and cooperable with a seat to control flow of gas from said lift gas port through said seat, a second pressure responsive member exposed on one side to said lift gas port and on the other side to said pilot valve seat, bleed means for bleeding fluid from the other side of said second pressure responsive member to said vent port when said pilot valve is closed, and two-position main valve means responsive to movement of said second pressure responsive member for alternately opening and closing said vent and lift gas ports.
 5. The apparatus of claim 4 wherein a mandrel is associated with said dip tube and a wire line retrievable housing carries said pressure responsive members and said main and pilot valves.
 6. A gas lift system comprising, a well having three conduits therein providing a production tubing and a vent tubing and a lift gas conduit, a crossover mandrel interconnecting the lower ends of the three conduits, a dip tube communicating with the lower end of the production tubing and extending downwardly therefrom, a sensing tube extending downwardly from the mandrel, means for bleeding a small amount of gas from the lift gas conduit into the sensing tube, an accumulator containing at least a portion of said dip tube and sensing tube, said accumulator communicating with the producing formation through a standing valve and with said mandrel, means establishing communication between said dip and sensing tubes within said accumulator, two-position valve means in said mandrel alternately communicating said vent tube and said lifting gas conduits with said accumulator, and means responsive to the differentials in pressure in said dip and sensing tubes at said mandrel for moving said valve means between said two positions.
 7. The system of claim 6 wherein a check valve in the dip tube adjacent the top of the accumulator permits flow of fluid from the dip tube to the vent tube.
 8. The system of claim 6 wherein the two-position valve means is responsive to a pressure responsive member which is exposed on one side to the lift gas conduit and on the other side to a chamber, a pilot valve is carried by said means responsive to a differential and controls flow of lifting gas to said chamber, and a bleed establishes communication between said chamber and said vent tube to bleed gas from said chamber when said pilot valve is closed.
 9. The system of claim 8 wherein the pressure responsive member, the means responsive to a differential, the pilot valve and the two-position valve means are carried in a wire line retrievable housing in said mandrel.
 10. The apparatus of claim 1 wherein the means for bleeding a small amount of gas comprises, a tapered seat, a spherical ball having a bore therethrough, resilient means holding said ball on its seat, and a stem extending through said bore in nonseating engagement therewith to leak a small amount of gas thereby, said stem reciproCating each time fluid communication is shifted between said vent and lift ports to prevent clogging of the passageway between said stem and bore through the ball.
 11. The apparatus of claim 4 wherein said second pressure responsive member comprises, a shaft, a sleeve slidable on the shaft, means sealing between the sleeve and shaft, said sleeve having a frusto-conical section, a seal member of tetrafluoroethylene surrounding said sleeve, said seal member having a frusto-conical bore section mating with said like section of said sleeve, means sealing between the large end of said sleeve and said seal member, and a support and guide ring carried by said shaft in sliding engagement with the small end of said sleeve and in abutment with the large end of the seal member, said second pressure response member arranged so that the pressure differential thereacross is always applied to the large end of said sleeve. 